The internal fixation systems, which are widely used in the orthopaedics sector, embrace different types of bone implants which are generally applied in order to stabilize the fractured bone site of a patient.
The internal fixation systems may comprise a bone plate, which is fixed in contact with an external surface of the fractured bone in order to ensure alignment and fixing of two or more segments thereof. In order to allow fixing of the plate, the system envisages in these cases a plurality of bone screws which pass through a corresponding number of holes formed in the element.
The internal fixation systems may also comprise an endomedullary, or intramedullary, nail which is typically inserted inside the medullary canal of the long bone of a patient. In this case also, generally one or more bone screws are provided, these passing through the bone cortex in the transverse direction and interfacing with the endomedullary nail in order to stabilize the system.
In both types of implant described above, it is required to provide a stable connection between the stem of the screw and the body of the plate or the nail. This connection must be able to transmit onto the plate/nail torsional and flexional stresses which are applied to the screw stem, allowing at the same time controlled axial sliding of said stem so as to allow the screwing and removal operations.
In order to satisfy the aforementioned requirements, connection systems are generally relatively elaborate and complex, so that they constitute a critical phase of the fixation system implant both from the point of view of time and as regards the attention required by the surgeon.
In particular, in the case of a fracture in the tranchanter zone, common practice requires stabilization of the fracture using one or more screws in the neck of the femur and several screws in the middle part of the femur. The screw placed in the neck of the femur usually is large in size and must be able to slide along its axis.
Therefore, the implant of the device requires the surgeon to carry out several consecutive operations aimed at ensuring the correct positioning of the screw inside the femoral neck.
Basically, the devices which are currently widely used require particular attention during insertion of the screw which is performed by means of a special tool, the orientation of which determines the correct insertion thereof into the patient's bone.
For instance, in document US 2014/214098 A1 it is disclosed an elongated modular implant which has a distal part and a proximal part both having a leading end and a trailing end, respectively. The trailing end of the distal part includes a tool engagement portion and the leading end of the proximal part includes a distal part engagement portion for an engagement with the tool engagement portion of the distal part. The implant further includes an assembly element for firmly coupling the distal part and the proximal part.
Consequently, the surgeon is required to carry out different preliminary operations before performing insertion of the screw.
Moreover, the connection of the screw to the plate/nail requires generally, after the aforementioned screw has been implanted, the insertion of a further locking element.
Such a surgical procedure must therefore be carried out with particular attention and unfortunately may not be assigned to surgeons with little experience, despite the fact that such operations are now considered to be routine in the orthopaedics departments of hospitals.
Moreover it is clear how this increases the duration of the operations, with greater risks for the health of patients, in particular if they are elderly.
A technical problem underlying the present disclosure is therefore that of providing an endosseous screw assembly and associated internal fixation system which allow a reduction in the duration of the surgical operations and which may be implanted by means of a limited number of operations carried out by the surgeon; at the same time it is also desirable that the operational methods should be those which are already known to the surgeon so as to be easily applied also by less expert surgeons.